Electrochemical sensor
An electrochemical sensor for detecting the concentration of ions in a solution includes a substrate, a sensor unit, and a reference electrode. The sensor unit includes at least one working electrode. The working electrode has a conductive layered structure formed on the substrate, and a sensor element of a metal oxide film formed on the conductive layered structure and capable of reacting with the ions in the solution to generate a potential. The reference electrode is spaced apart from the working electrode, and includes a conductive film printed on the substrate for establishing a potential difference between the working electrode and the reference electrode when the electrochemical sensor is brought into contact with the solution.
This application claims priority of Taiwanese Application No. 099105632, filed on Feb. 26, 2010.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to an electrochemical sensor, more particularly to an electrochemical sensor including a substrate formed with a reference electrode and a working electrode thereon.
2. Description of the Related Art
U.S. Patent Application Publication no. 2009/0021263 discloses an electrochemical system that includes a multi-ion potential sensor and a solid-state reference electrode. As illustrated in
An object of the present invention is to provide an electrochemical sensor including a working electrode and a reference electrode which are formed on a substrate and which cooperate with each other to provide satisfactory sensitivity and linearity in detection of the concentration of ions of interest in a solution.
According to this invention, there is provided an electrochemical sensor for detecting the concentration of ions in a solution. The electrochemical sensor includes a substrate, a sensor unit, and a reference electrode. The sensor unit includes at least one working electrode. The working electrode has a conductive layered structure formed on the substrate, and a sensor element of a metal oxide film formed on the conductive layered structure and capable of reacting with the ions in the solution to generate a potential. The reference electrode is spaced apart from the working electrode and includes a conductive film printed on the substrate for establishing a potential difference between the working electrode and the reference electrode when the electrochemical sensor is brought into contact with the solution.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which:
Before this invention is described in greater detail with reference to the accompanying preferred embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure.
Referring to
The conductive film 31 of the reference electrode 3 is made from a material selected from the group consisting of iron, copper, carbon, silver, silver chloride, indium tin oxide, zinc and tin. Preferably, the conductive film 31 is made from silver paste. Alternatively, the conductive film 31 of the reference electrode 3 may include a first layer of silver paste printed on the substrate 1, a second layer of carbon paste printed on the first layer, and a third layer of silver paste printed on the second layer.
The conductive layered structure 211 of the working electrode 21 includes at least one layer made from a material selected from the group consisting of iron, copper, carbon, silver, silver chloride, indium tin oxide, zinc and tin. Preferably, the conductive layered structure 211 includes a layer of silver paste. Alternatively, the conductive layered structure 211 may include a first layer of silver paste printed on the substrate 1, and a second layer of carbon paste printed on the first layer. The sensor element 212 is formed on the second layer.
Preferably, the metal oxide for forming the sensor elements 212 is tin oxide.
The conductive trace 213 of the working electrode 21 is used to electrically connect the conductive layered structure 211 to a measuring system (not shown). The reference conductive trace 32 is used to electrically connect the conductive film 31 of the reference electrode 3 to the measuring system.
The conductive trace 213 of the working electrode 21 and the reference conductive trace 32 of the reference electrode 3 include at least one layer made from a material selected from the group consisting of iron, copper, carbon, silver, silver chloride, indium tin oxide, zinc and tin. Preferably, the conductive trace 213 of the working electrode 21 and the reference conductive trace 32 of the reference electrode 3 are made from silver paste. Alternatively, the conductive trace 213 of the working electrode 21 and the reference conductive trace 32 of the reference electrode 3 may include a first layer of silver paste printed on the substrate 1, a second layer of carbon paste printed on the first layer, and a third layer of silver paste printed on the second layer.
The substrate 1 may be made from a flexible and insulating material, such as polyethylene terephthalate.
The number of the working electrodes 21 may be changed according to requirements of the actual application.
Referring to
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It is noted that the sensor elements 212 of the working electrodes 21 may be made from the same material or different materials depending on the actual requirements.
Example 1The electrochemical sensor of Example 1 has the same configuration as that of the seventh preferred embodiment. For Example 1, the substrate 1 is made from polyethylene terephthalate; each of the conductive layered structures 211 and the conductive traces 213 of the working electrodes 21 is comprised of a first layer of silver paste and a second layer of carbon paste printed on the first layer; the conductive film 31 is made from a layer of silver paste, and the reference conductive trace 32 is comprised of a first layer of silver paste and a second layer of carbon paste printed on the first layer; the insulating film 4 is made from epoxy resin; and the sensor elements 212 are made from tin oxide.
Comparative Example 1The electrochemical sensor of Comparative Example 1 includes a multi-ion potential sensor and the aforesaid solid-state reference electrode. The multi-ion potential sensor has a configuration differing from that of the electrochemical sensor of Example 1 in that the former is dispensed with the reference electrode 3.
[Test]Linearity and sensitivity of the electrochemical sensor were determined based on measured output potentials (mV) in response to different predetermined pH values of the buffer solutions, in which the sensitivity is calculated using the following equation:
Sensitivity (mV/pH)=(the highest output potential−the lowest output potential)/(the highest pH value−the lowest pH value)
Referring to
The results of the linearity and the sensitivity of the electrochemical sensor using one sensor element 212 over the pH values ranging from 2 to 12 are listed in Table 1.
(Test 2) Linearity and Sensitivity Determined Using Four Sensor Elements in Each pH MeasurementThe measurement of the linearity and the sensitivity in Test 2 is similar to that in Test 1, except that, in Test 2, the number of the sensor elements 212 used in each pH measurement was four, and the conductive traces 213 corresponding to the four selected ones of the sensor elements 212 of the working electrodes 21 were electrically connected to the positive input ends (+) of four instrumentation amplifiers AD. The potential signals collected from the instrumentation amplifiers AD were processed by an adder so as to generate output signals, which were transmitted to and were converted through the digital measuring system HP34401A into digital signals for calculation of the linearity and the sensitivity of the selected sensor elements 212 through the computer. The results of the linearity and the sensitivity of the electrochemical sensor using four sensor elements 212 over the pH values ranging from 2 to 12 are listed in Table 1.
(Test 3) Linearity and Sensitivity Determined Using Eight Sensor Elements in Each pH MeasurementThe measurement of the linearity and the sensitivity in Test 3 is similar to that in Test 2, except that, in Test 3, the number of the sensor elements 212 used in each pH measurement was eight. The results of the linearity and the sensitivity of the electrochemical sensor using eight sensor elements 212 over the pH values ranging from 2 to 12 are listed in Table 1.
Referring to
The results shown in Table 1 indicate that the electrochemical sensor of this invention can significantly improve the sensitivity as compared to the conventional electrochemical system.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements.
Claims
1. An electrochemical sensor for detecting the concentration of ions in a solution, comprising:
- a substrate;
- a sensor unit including at least one working electrode having a conductive layered structure formed on said substrate and a sensor element of a metal oxide film formed on said conductive layered structure and capable of reacting with the ions in the solution to generate a potential; and
- a reference electrode spaced apart from said working electrode and including a conductive film printed on said substrate for establishing a potential difference between said working electrode and said reference electrode when said electrochemical sensor is brought into contact with the solution.
2. The electrochemical sensor of claim 1, wherein said conductive film is made from silver paste.
3. The electrochemical sensor of claim 1, wherein said conductive layered structure includes a layer of silver paste.
4. The electrochemical sensor of claim 1, wherein said conductive layered structure includes a first layer of silver paste printed on said substrate, and a second layer of carbon paste printed on said first layer, said sensor element being formed on said second layer.
5. The electrochemical sensor of claim 1, wherein said metal oxide is tin oxide.
6. The electrochemical sensor of claim 1, wherein said sensor unit includes a plurality of said working electrodes, said conductive film of said reference electrode being bar-like in shape and extending in a direction, said sensor elements of said working electrodes being disposed adjacent to said conductive film and being distributed along the direction.
7. The electrochemical sensor of claim 1, wherein said sensor unit includes a plurality of said working electrodes, said conductive film of said reference electrode being circular in shape, said sensor elements of said working electrodes being disposed adjacent to said conductive film and being angularly displaced from one another to surround said conductive film.
8. The electrochemical sensor of claim 1, wherein said sensor unit includes a plurality of said working electrodes, said conductive film of said reference electrode being circular in shape and being formed with a plurality of inner spaces that are angularly displaced from one another, said sensor elements of said working electrodes being disposed in said inner spaces in said conductive film.
9. The electrochemical sensor of claim 1, wherein said sensor unit includes a plurality of said working electrodes, said conductive film of said reference electrode being arch-like in shape, said sensor elements of said working electrodes being disposed adjacent to said conductive film and being angularly displaced from one another.
Type: Application
Filed: Aug 23, 2010
Publication Date: Sep 1, 2011
Inventors: Tai-Ping Sun (Jhongli City), Chung-Yuan Chen (Sinhua Township), Hsiu-Li Shieh (Taichung City), Tak-Shing Ching (Taichung City)
Application Number: 12/805,888
International Classification: G01N 27/26 (20060101);